Huge 'mega-colonies' of penguins have been discovered near the Antarctic peninsula, hosting more than 1.5m birds. Researchers say it shows the area is a vital refuge from climate change and human activities and should be protected by a vast new marine wildlife reserve currently under consideration. The Adélie penguins were discovered on the Danger Islands in the Weddell Sea, on the east side of the Antarctic peninsula.

On an expedition to an icy island chain the Danger Islands off the Antarctic Peninsula’s northern tip, researchers discovered a massive supercolony of more than 1.5 million Adélie penguins, according to a study published March 2 in Scientific Reports. Scientists had known of an Adélie penguin colony (Pygoscelis adeliae) but satellite images revealed more guano on the rocky islands than could be explained by the colony’s expected numbers.

It is also the only island to date with a population estimate (285,000–305,000) derived from a ground survey of the island. While a previous geological expedition30 noted the presence of Adélie penguins on all of the Dangers Islands (with the exception of Darwin Island, which was not visited), the presence of Adélie penguins on several of these islands went largely unrecognized until a recent Landsat satellite survey of the Antarctic identified several large penguin colonies supporting what appeared to be nearly 200,000 Adélie penguin nests.

Even though the tiny island chain is only about 10 kilometers across, researchers hadn’t realized the extent of the pengube.com/embed/EWtvsWSwmrs" frameborder="0" allow="autoplay; encrypted-media" allowfullscreen></iframe>in population, says study coauthor Heather Lynch, an ecologist at Stony Brook University in New York. “In the Antarctic, distances are so vast, something major could be just around the corner and you wouldn’t know.”

The researchers did a preliminary head count, took drone images and collected mud cores during a 2015 expedition. The team then spent about a year using a computer algorithm to analyze the images to more fully count 751,527 penguin nests, Lynch says. For every nesting bird, the scientists assumed there was a partner penguin out at sea.

Elsewhere in Antarctica where the climate is more volatile, penguin colonies are in decline. “I hope this provides impetus for a marine protected area in the Danger Islands with expanded borders from what has been proposed,” Lynch says.